Black powder manufacture



' '1 1939- c. w. BROOKS, JR 2, 6 ,0

BLACK POWDER mmumcwunn Filed Feb. 24, 1957 WHEEL/N6 SCREENING 7'0GPANULATE PREDRY/NG STEP PRESS/N6 INTO Pt'LLET FORM AT HIGH DENJ/T)CLARENCE W BROOKS, J'rr. INVENTOR.

A TTORNEY.

Patented Aug. 1, 1939 BLACK POWDER MANUFACTURE Clarence W. Brooks, .lr.,Wenonah, N. J., assignor to E. I. du Pont de Nernours & Company,Wilmington, Dcl., a corporation of Delaware Application February 24,1937, Serial No. 127,401

10 Claims.

This invention relates to an improved process for producing pellets orblocks of black blasting powder having a relatively high density.

Black blasting powder, compressed into the form of cylindrical pelletsor blocks, has been introduced into practice with considerable successwithin the last few years, this form of powder largely replacing theglazed granular black blasting powder previously used. Such pressedpowder commonly comprises pellets about 2 inches in length and withdiameters varying from 1 to 2 inches. Four of the above pellets of2-inch length are ordinarily enclosed end to end in a paper wrapper.This package resembles a stick or cartridge of dynamite and may readilybe loaded into a borehole.

These pellets commonly have the ordinary black powder composition, forexample 72% sodium nitrate, 12% sulfur, and 16% charcoal, blended bythorough incorporation of the ingredients in the customary edge runnerwheel mills. The product of such incorporation is known as wheel cake.Wheel cake is the incorporated powder base which is subsequentlyprocessed through several intermediate stages for the purpose ofobtaining the finished forms in which all black blasting powders arecustomarily used.

The prior art methods of producing black powder pellets of relativelyhigh density have commonly utilized the product known as green grain asthe material for pressing. By high density is meant an apparent densityof 1.45 to 1.60, such that there will be 115 to 105-l 8" cartridges per50 pounds. Green grain is produced by first pressing wheel cake intoslabs of high density, approximately 2 feet square and 1 inch thick,

this material being designated by the industry as.

press cake, having a density of 1.70 to 1.80. The press cake is thencorned to a granulation suitable for pressing into pellets. A suitablegranulation is that passing through an opening of 0.115 inch and held ona screen having openings of 0.046 inch. Green grain produced in thismanner is characterized by a high density, 1.7 to 1.8, and possesses ahard, clean, grainy structure. Pellets are produced from this materialby feeding it into a mechanical press where it is given the desiredcylindrical shape and a center hole is provided running longitudinallythroughout the pellet, for example in diameter.

It will be seen, therefore, that prior art methods of producing highdensity pellets have had to start with a form of powder that has alreadybeen given considerable treatment. While screened wheel cake has beenemployed for direct compression into pellets, as disclosed by Brooks andJohnson, in United States Patent No. 2,062,636, such pellets have beencharacterized by low density, for example between 1.3 and 1.4, such that130 to 120 cartridges are contained in a 50-pound box. It has been foundto be impossible to produce by this or any other method known to theprior art, high density pellets directly from wheel cake which possesssatisfactory burning speeds.

Pellets of varying density are required in different types of blastingand on different occasions, and considerable advantage would result insimplicity of operations if high density pellets could be produceddirectly from wheel cake.

An object of the present invention is an improved process for producinghigh density black powder pellets. A further object is such a methodwherein increased simplicity and safety in operations is obtained. Astill further object is a method for the production of black powderpellets of relatively high density and satisfactory high burning speedsdirectly from wheel cake. Additional objects will be disclosed as theinvention is further described hereinafter.

I have found that the foregoing objects are accomplished by the processof the present invention, which comprises subjecting wheel cake to apreliminary drying process and afterwards compressing into a pellet formof high density.

As a result of this process, high density pellets may be prepareddirectly from wheel cake, yet possessing the desired high burningspeeds. The beneficial effect of the predrying step upon the burningspeed of the resulting pellet is directly proportional to the amount ofdrying.

My preferred process may be more readily understood by referring to theaccompanying drawing which constitutes a flow sheet showing in preferredsequence the steps of forming the wheel cake, screening said wheel caketo granulate the same and to remove the fines therefrom, passing thewheel cake, granulated by said screening, through a predrying step, andpressing said predried granules into pellet form at high density;namely, at densities of at least 1.40. It will be noted that the veryimportant and novel step about which the invention centers; namely, thepredrying step, has been emphasized in the flow sheet by means of adouble line.

I prefer to use the following procedure. The black powder composition isincorporated under the wheels at a moisture content between 6 and 10%,preferably about 6.5%. The moist wheel cake is first screened somewhatto produce a more or less granular product. It is then desirable toreduce the bulkiness of this granular product. This can be accomplishedby the removal. of the dust and a portion of the finer particles, forexample by passing all the material through a 4- mesh screen andutilizing the portion that is held on a 16-mesh screen. This wheel cakeis then dried to a moisture content between 1.5 and preferably between 2and 3%. This wheel cake which has been subjected to a preliminary.

drying is then pressed in the pellet press. The pellets are subsequentlydried to a moisture content lower than 1% and preferably to less than0.5%. These pellets have a density comparable to that of the highdensity pellets of the prior art, for example 1.40 to 1.65. Furthermore,the pellets thus produced possess much more satisfactory high burningspeeds than do pellets produced directly from wheel cake with theomission of the drying step. This result maybe illustrated bythefollowing table, which shows a comparison with respect to burning timeof high density pellets produced from corned press-cake, grained wheelcake, and predried wheel cake grain respectively. The density is statedin terms of cartridges per 50 pounds of powder. The pellets employed inthese measurements were 2 inches in length and 1 inches in diameter.

Burning timeseconds Density, ctgs./50 lbs. Corned Grained 5 5352 5 2press-cake wheelcake grain l.4tol.8 2.213026 l0tol.4 2.0t0 2.4 1.8to 2.2

It becomes apparent from these results that by the process of thepresent invention pellets are produced which display burning speedsasrapid as those produced from corned press-cake at comparabledensities. Further, it may be noted that the preferred process producespellets which have higher burning speeds than those produced directlyfrom wheel cake without employing the drying step and indeed,the'burning speeds are even higher than those of pellets pressed to alower density by this latter'process. This result is unexpected in viewof the general principle for pelleted black powder compositions thatspeed of burning decreases as density increases. As shown, pelletsproduced directly from wheel cake without preliminary drying at adensity of 110 cartridges per 50 pounds require much longer burning timethan pellets from predried wheel cake grain at the higher density of 106cartridges per 50 pounds. r

The above preferred method may be varied in several ways. For instance,instead of screen ing and removing the fines prior to the drying step,the moist wheel cake may be dried directly. It is then desirable toscreen the wheel cake and reduce the bulkiness thereof by removing thefines immediately after drying. Again, the wheel cake may be simplyscreened either before or after the drying steps without the removal ofthe fines. In other words, although the chief benefits of the inventionare derived from the step of predrying prior to pressing, these benefitsare increased by supplementing this drying step with the auxiliaryoperations of screening and reduction of bulk.

The method outlined in the foregoing makes possible to the art for thefirst time the production of high density black powder pellets ofsatisfactory high burning speed, directly from wheel cake and has anumber of other advantages over those heretofore in use for theproduction of high density pellets. By the direct use of wheel cake, theprocedures of pressing the wheel cake and passing the cut press cakethrough a coming mill are eliminated. This is a distinct safetycontribution to the process, since definite hazards are associated withthe operation of press and corning mills. It means also a simplifying ofblack powder pellet manufacturing procedure by cutting out the two stepsnamed.

The pellets, asformed in the press, will desirably be of the usualcylindrical form, with the central perforation longitudinally throughthe pellet. These pellets, as stated, are customarily of 2-inch lengthand of varying diameters from 1 to 2 /2 inches, four of these pelletsbeing wrapped end to end in a paper wrapper to form an, 8-inchcartridge. My invention is not limited necessarily, however, to suchproducts. The powder may, for example, be compressed into anypredetermined form.

My improved process of manufacturing high density pellets has beendescribed in detail in the foregoing. It should be understood, however,that many variations in procedure and in minor points may be adoptedwithout departure from the scope of the invention. I Wish,therefore,,1to be limited only by the following patent claims:

I claim:

1. The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises subjecting the wheelcake to a preliminary drying step and compressing said dried wheel caketo a density of at least 1.40.

2. The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises screening vsaid wheelcake, subjecting said screened wheel cake to a preliminary drying stepand compressing said screened, dried wheel cake into a container ofpredetermined form at a density of at least 1.40.

3. The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises screening said wheelcake, removing the fines therefrom, subjecting said screened wheel caketo a preliminary drying step/and compressing said screened, dried wheelcake into a container of predetermined form at a density of at least1.40.

'4. "The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises subjecting said wheelcake to a preliminary drying step, screening said dried wheel cake, andcompressing said dried, screened wheel cake into a container ofpredetermined format a density of at least 1.40.

5.'The' process of producing high density pellets of black blastingpowder from Wheel cake, which process comprises subjecting said wheelcake to a preliminary drying step, screening said dried wheel cake andremoving the fines therefrom, and compressing said dried, screened wheelcake into a container of predetermined form at a density of at least1.40.

6. The process of producing high density pellets of black blastingpowder'from wheel cake, whichpprocess comprises subjecting the wheelcaketo a preliminary drying step and compressing saiddriedwheel cake toa density greater than 1.40 in a container'of predetermined form. 75

'7. The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises predrying said wheelcake to a moisture content between 1.5 and 5%, and compressing saiddried wheel cake into a container of predetermined form at a density ofat least 1.40.

8. The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises predrying said wheelcake to a moisture content between 1.5 and 5%, compressing said driedwheel cake into a container of predetermined form at a density of atleast 1.40, and imparting a still harder surface to said pellet powderby drying to a moisture content below 1.0%.

9. The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises screening said wheelcake, predrying the same to a moisture content between 1.5 and 5%, andcompressing said dried wheel cake into a container of predetermined format a density of at least 1.40.

10. The process of producing high density pellets of black blastingpowder from wheel cake, which process comprises subjecting wheel cakehaving a moisture content between 6.0 and 10% to a preliminary dryingstep wherein. said powder is dried to a moisture content between 1.5 and5%, and compressing said dried wheel cake into a container ofpredetermined form at a density of at least 1.40.

CLARENCE W. BROOKS, JR.

